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From 09fd0a6123a72bd1e71635d4941ba591ef5ff7fe Mon Sep 17 00:00:00 2001
From: Shirish S <shirish.s@amd.com>
Date: Fri, 11 Mar 2022 20:30:17 +0530
Subject: amd/display: set backlight only if required
Git-commit: 4052287a75eb3fc0f487fcc5f768a38bede455c8
Patch-mainline: v5.18-rc2
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225

[Why]
comparing pwm bl values (coverted) with user brightness(converted)
levels in commit_tail leads to continuous setting of backlight via dmub
as they don't to match.
This leads overdrive in queuing of commands to DMCU that sometimes lead
to depending on load on DMCU fw:

"[drm:dc_dmub_srv_wait_idle] *ERROR* Error waiting for DMUB idle: status=3"

[How]
Store last successfully set backlight value and compare with it instead
of pwm reads which is not what we should compare with.

Signed-off-by: Shirish S <shirish.s@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 7 ++++---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h | 6 ++++++
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 5895afefccb7..62139ff35476 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -3973,7 +3973,7 @@ static u32 convert_brightness_to_user(const struct amdgpu_dm_backlight_caps *cap
 				 max - min);
 }
 
-static int amdgpu_dm_backlight_set_level(struct amdgpu_display_manager *dm,
+static void amdgpu_dm_backlight_set_level(struct amdgpu_display_manager *dm,
 					 int bl_idx,
 					 u32 user_brightness)
 {
@@ -4004,7 +4004,8 @@ static int amdgpu_dm_backlight_set_level(struct amdgpu_display_manager *dm,
 			DRM_DEBUG("DM: Failed to update backlight on eDP[%d]\n", bl_idx);
 	}
 
-	return rc ? 0 : 1;
+	if (rc)
+		dm->actual_brightness[bl_idx] = user_brightness;
 }
 
 static int amdgpu_dm_backlight_update_status(struct backlight_device *bd)
@@ -9948,7 +9949,7 @@ static void amdgpu_dm_atomic_commit_tail(struct drm_atomic_state *state)
 	/* restore the backlight level */
 	for (i = 0; i < dm->num_of_edps; i++) {
 		if (dm->backlight_dev[i] &&
-		    (amdgpu_dm_backlight_get_level(dm, i) != dm->brightness[i]))
+		    (dm->actual_brightness[i] != dm->brightness[i]))
 			amdgpu_dm_backlight_set_level(dm, i, dm->brightness[i]);
 	}
 #endif
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
index 6a908d736d6a..7e44b0429448 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
@@ -540,6 +540,12 @@ struct amdgpu_display_manager {
 	 * cached backlight values.
 	 */
 	u32 brightness[AMDGPU_DM_MAX_NUM_EDP];
+	/**
+	 * @actual_brightness:
+	 *
+	 * last successfully applied backlight values.
+	 */
+	u32 actual_brightness[AMDGPU_DM_MAX_NUM_EDP];
 };
 
 enum dsc_clock_force_state {
-- 
2.38.1